1. Field of the Invention
The invention relates to a brightness intensifier tube, comprising an entrance screen, an exit screen and an electron-optical system for imaging electrons emanating from the entrance screen onto the exit screen.
2. Description of Related Art
When brightness intensifier tubes or the type referred to above are used in, for example sights, use is made of an alignment marker. From U.S. Pat. No. 4,582,400 it is known to project, using an optical system, an alignment marker of this kind into the optical beam path of a sight comprising a brightness intensifier tube. Furthermore, from U.S. Pat. No. 4,721,375 it is known to arrange a support provided with an alignment marker in the optical beam path of the sight so as to be adjustable therein.
Both solutions have the drawback that the alignment marker must be individually adjusted in each sight and must each time be readjusted after misalignment, for example caused by shocks and the like. For adjustment and readjustment of the alignment marker, therefore, a comparatively expensive optical and mechanical adjustment mechanism, respectively, is required for each sight.